Process of producing graphite in colloidal form.



UNITED TATE PATENT @EFJICE.

HANS KARPLUS, 0F BERLIN, GERMANY.

PROCESS OF PRODUCING GRAPHITE IN COLLOIDAL FORM.

No Drawing.

To all whom it may concern Be it known that I, Dr. HANS KAnrLUs, a citizen of Austria, residing at 36 Schtineberger Ufer, Berlin, in the German Empire, have invented new and useful Improvements in Processes of Producing Graphite in Colloidal Form, of which the following is a specification.

This invention relates to the production of graphite in colloidal form and has for its object to provide a process that is simple and yields good results.

It is known that certain kinds of those artificial graphites that are produced in the electric furnace may be deflocculated and converted into a colloidal soluble form through treatment with aqueous solutions of tannin or similar organic substances. However, when such a method is applied on other kinds of graphite, especially graphites as found in nature, a very small or no yiel at all of colloidal graphite is obtained.

According to the present invention it is possible to split even native graphite into ultra-microscopical particles by subjecting the graphite to a stronger loosening process, viz. to peptonization. The bodies to be split up, on being peptonized are converted partly into compounds soluble in water, and partly into gaseous compounds. When the peptonizing agents are applied in comparatively small quantities, then only a fraction of the body to be disintegrated will dissolve or be transformed into a gas, while the main portion will remain behind undissolved but in a highly dispersed condition.

On treating ordinary graphite with strong oxidizing agents the process, under certain conditions, may be so conducted that only such oxidation products of the graphite are obtained that are soluble in water or are in the gaseous state. When graphite is mixed with concentrated sulfuric acid, and solid permanganate of potassium is added, the formation of graphitic acid, insoluble in water, starts even at ordinary temperature. However, if in such a case the process of oxidation is not carried on at ordinary temperature but is allowed to proceed to a higher temperature then, besides the graphitic acid, carbon monoxid and carbon dioxid and other oxidation products soluble in water areproduced which are related to mellitic acid. The gaseous oxidation products and those that are soluble in water increase the higher the temperature is. If the Specification of Letters Patent.

Patented Mar. 21, 1916.

Application filed June 26, 1915. Serial No. 36,570.

graphite consists of approximately equally sized particles the formation of graphitic acld wlll be lmost completely absent at a certain temperature in consequence of the fact that from this temperature upward the graphltic acid primarily formed is immediately further oxidized to oxidation products soluble in water. The same phenomenon appears on application of other oxidizing mlxtures. If Brodies oxidizing mixture (KClO +fuming HNO is used, the temperature above which the formation of graphitic acid is negligible is higher than if IQMDO +H SO is used, and it is lower with CrO +conc. H 80 In any case the temperature above mentioned is lower the more finely crystallized the graphite used is, so that with graphites the grains of which have equal volume and are sufiiciently fine the oxidation process may proceed at ordinary temperature withoutdthe danger of formation of graphitic aci The process according to this invention consists in allowing the said oxidizing mixtures to act upon the graphite to be split up at temperatures at which no perceptible formation of graphitic acid occurs, and in proportioning the oxidizing agent so that only a small quantity of the graphite is lost as gaseous oxids of carbon, or as oxidation products soluble in water. In most cases so small a proportion of the oxidizing agent suffices that at the utmost but 5 to 10 per cent. of the graphite acted upon could be oxidized to gaseous-oxids of carbon.

The process may be carried out either so that the graphite is mixed with the strong acids, and the oxidizing substance is adde in solid form; or the oxidizing agents may with equal success be dissolved in the aci completely or partly whereafter the graphite is added in portions while the mixture is being stirred. The temperature at whic the oxidation must proceed depends, as previously stated, upon the size of the particles of graphite used and will have to be determined by tests in each case. After the 0x1- dation has suiiiciently proceeded the graphite is separated by mechanical means. To

facilitate the separation the mixture prothe mechanical deposition process, may be duced by the reaction is preferably diluted separated in any known manner, for in- With water. A washing with water, prefstance by a filtering or centrifugal action, erably distilled water, follows, till the which, if desired,may be preceded by a cographite can be so dispersed in distilled agulation of the mass through the action of 70 water as to produce a brown solution reanelectrolyte. sembling a colloidal silver solution. The The product obtained by the process is graphite thus obtained is free of oxidation primarily intended to be used as a lubricant. products, especially freeof graphiteic acid, Example: 1 kilogram of native graphite if the peptonization is carried on at the having been rid of its ash constituents in 75 proper temperature. A small sample any known manner, is mixed with 3 kilobrought to red heat neither shows developgrams of concentrated sulfuric acid. While ment of gases or those inflation'phenomena the mixture is being stirred 150 grams of characteristic to the presence of graphitic permanganate'of potassium, or 200 grams acid. Should the dispersed graphite contain of sodium dichromate, or an equivalent mix- 0 graphitic acid this may be decomposed by ture of both of these substances, are added heating the graphite with concentrated sulin the solid state. After a few days about furic acid to from 160 to 180 centigrade in 300 grams of water are added, which addicase the graphitic acid, if present, would be tion has been found of advantage but is not likely to interfere with the further use of a requisite. Thereupon a further quantity as the graphite. of 150 grams of permanganate of potassium, As oxidizing agents solutions or mixtures or 200 grams of dichromate, are added. of permanganates, for instance, permanga- The single operations may be carried out Date of potassium, of chromic acid, chroalso atthe same time. Theoxidation being mates perchromates, chlorates, or perchlosufliciently advanced, which may be ascer- 9o rates in H SO or HNO are suitable. Also tained by testing the hydrosol, the entire mixtures of lPbO with HNO and MnO mass is poured into 10 liters of water. with H orHNO may be used. Thereafter the graphite is drawn OE and The various oxidizing agents may be apwashed with distilled water. To separate 30 plied in mixture, or successively. Fuming those non-colloidal constituents which may nitric acid does not produce the desired disstill be contained in the graphite, the peppersing action. To prevent aflocculating of tonized graphite is then thoroughly disthe hydrosol through the action of elecseminated in a solution of 50 grams saponin trolytes or carbonic acid of the air, the hyin about 10 liters of water. Finally, the 35 drosol produced may be stabilized in known whole mass is subjected to a mechanical 10o manner by means of protecting colloidsdeposition process. The hydrosol obtained For that purpose quite small proportions of is separated from the sediment in well gelatin, albumin, decomposition products of own manner. albumin, gum arabic, and the like may be What I claim is: e0 dissolved in the hydrosol. 1. The process of producing graphite in Since the native graphite of the trade, as colloidal form, consisting in peptonizing a, rule, can but partly be converted into a graphite with strong oxidizing agents and highly dispersed form by the peptonization thereafter washing the products of the reprocess, it is necessary to separate the action. t5 highly dispersed constituents from those 2. The process of producing graphite in that are not sufliciently split up. colloidal form, consisting in subjecting For obtaining the highly dispersedzgraphgraphite to the peptonizing action of strong ite constituents it is necessary to apply a oxidizing agents at a temperature at which fractionating elutriation which can be carthe formation of graphitic acid is substan- 0 ried on in pure water. Preferably the 8111- tially absent, which temperature is pretriation is carried on in aqueous solutions viously determined for the particular size of of organic compounds capable of afiectlng granules by tests, and thereafter washing the capillary action of the solvent asfor exth rodu t of the re ction, ample nonelectrolytes such as the dryr0ph- 3. The process of producing graphite in ilous colloids albumin, .peptone, gelatin, colloidal form, consisting in subjecting 12o tragacanth, agar, gum, glue, saponin, cycla- ,graphite to the peptonizing action of strong min amygdalin, and the like, which reduce oxidizing agents thereafter washing the t 6 Surface tension o the 801mm NOII- products of the reaction and finally separatcolloidal substances, too, may be used, as ing. the highly dispersed constituents from for instance amyl. alcohols. As against an the less highly dispersed particles by an elutriation in pure water, an elutriation carelutriation treatment. ried on in such solutions as specified above 4. The process of producing graphite in allows of a more distinct fractionation with colloidal form, consisting in peptonizing regard to the size of the particles. Those graphite with strong oxidizing agents at a constituents that'remain in suspension after temperature at which the formation of graphitic acid is substantially absent, which temperature is previously determined for the particular size of granules by tests, thereafter washing the products of the reaction, and finally separating the highly dispersed constituents from the less highly dispersed particles by an elutriation treatment.

5. The process of producing graphite in colloidal form consisting in peptonizing graphite with strong oxidizing agents, thereafter washing the products of the reaction and finally separating the highly dispersed constituents from the less highly dispersed particles by an elutriation in an aqueous solution of organic non-electrolytes capable of decreasing the surface tension of the water.

6. The process of producing graphite in colloidal form consisting in peptonizing graphite with'strong oxidizing agents at a temperature at which the formation of graphitic acid is substantially absent, which temperature is previously determined for the particular size of granules by tests, thereafter washing the products of the reaction and finally separating the highly dispersed constituents from the less highly dispersed particles by elutriation in an aqueous solution of organic non-electrolytes capable of decreasing the surface tension of the water.

colloidal form consisting in peptonizing graphite with strong oxidizing agents,

thereafter washing the products of the reaction and finally separating the highly dispersed constituents from the less highly dispersed particles by an elutriation in an aqueous solution of organic non-electrolytes, which are hydrophilous colloids and capable of decreasing the surfacetension of the water.

8. The process of producing graphite in colloidal form consisting in peptonizing graphite with strong oxidizing agents at a temperature at which the formation of graphitic acid is substantially absent, which temperature is previously determined for the particular size of granules by tests, thereafter washing the products of the reaction and finally separating the highly dispersed constituents from the less highly dispersed particles by elutriation in an aqueous solution of organic non-electrolytes, which are hydrophilous colloids and capable ofvdecreasing the surface tension of the water.

In witness whereof I have signed my name in the presence of two subscribing witnesses.

DR. HANS KARPLUS.

Witnesses WOLDEMAR HAUPT, HENRY HAsPER. 

